1. Field of the Invention
The present invention relates to an improvement in or relating to adjustment of a travel route detecting device for use in a vehicle, and more particularly to an improved method of adjusting a rate-type travel route detecting sensor for use in an automobile and the like.
2. Description of the Prior Art
As an efficient aid for a driver of an automotive vehicle or the like to avoid losing his way while driving at night or in unfamiliar surroundings away from his desired route of travel, there have been developed a variety of apparatus which are designed to visually indicate continuously or discretely a due current position or similar information relating to the vehicle by way of an indication panel or display screen including a related road map or the like disposed at the driver's seat so that he may fully receive a necessary ready guidance relating to the vehicle's current status of travel with respect to the desired course of travel.
In the conventional travel route indicating apparatus for such an application, a current bearing and quantity of azimuthal deviation of the vehicle are detected by a bearing detecting section which employs a rate-type gyroscope, a gas rate sensor or the like adapted to detect a possible angular velocity produced about the axis of yawing motion of the vehicle, the gate rate sensor being a typical means for detecting an azimuthal motion of the vehicle. The gas rate sensor is specifically designed to detect an angular velocity produced from a turning motion of the vehicle in terms of a fractional or fine amount of difference in the sensed heat factor as generated by a possible change in the gas flow within the gas rate sensor from an azimuthal deviation such as generated in the turning motion of the vehicle, wherein a current location of the vehicle along its travel route is obtained from an arithmetic operation on the thus-obtained data, and the results of this arithmetic operation are stored in sequence, and indicated visually by way of spot information varying from time to time on a display screen upon which there is presented a transparent road map of routes or roads along which the vehicle travels in cruising operation. In the installation of such gas rate sensor onto the automotive vehicle's body, because it is subjected to incessant and irregular vibrating motions as caused during the travelling motion of the vehicle, there inevitably exists undesirable drift in the detection of a current rate of yawing motion in the body of the automobile. With the employment of such conventional gas rate sensor as it is, it is very possible that spot information showing a current orientation of the vehicle on the display would deviate from a predetermined course of travel due to a thusfar accumulated quantity of error in detection as created from a possible drift in the operation of the gas rate sensor during travel with many turns to such an extent that such information relating to the vehicle's location would indicate an erroneous location on the display. Therefore, it becomes extremely difficult or even impossible for the vehicle's driver in practice to determine whether the displayed information on the display is erroneous or his vehicle is actually travelling in a different or wrong way, thus causing substantial ambiguity.
In this respect, according to the typical conventional construction of a travel route indicating apparatus for use in an automotive vehicle, a current value of the rate of yawing motion of the vehicle is detected each time the vehicle stops, and the thus-obtained value of drift is simply to be subtracted from an output of the rate sensor as obtained in subsequent travel of the vehicle, thereby providing sequential adjustment of the zero-level of the detection value from the yawing rate as obtained in the rate sensor.
With such a manner of adjustment of the zero-level in the detection of yawing rate by way of the conventional rate sensor arrangement, it is to be noted that there would be produced a relatively large output signal representing yawing rate from the rate sensor such as at a moment immediately after the vehicle stops or starts with a substantial amount of vibrating motion in the vehicle's body. With such an extraordinary output of detection of yawing rate, however, being subtracted from a subsequent output of the rate sensor in the normal running operation, it is natural that there would inevitably be produced a substantial amount of error in this particular zero-level adjustment per se.
In addition, even when the automotive vehicle is stopping, there would occur similar situations providing a relatively large output of yawing rate detection with a possible swing motion of the vehicle's body as generated by instances such as a sudden gust of wind, a slam of a door, a contingent quick turning of the steering wheel, etc.
The present invention is essentially directed toward overcoming such inconveniences and difficulties as experienced in the conventional design of a visual travel route indicating apparatus which incorporates a gate rate sensor.